iPhones have had controller support baked right into the operating system since iOS 7 launched last year, but the pickings are still slim and developers have yet to adopt any widespread support of these devices.

So how are iPhone gaming enthusiasts to decide what iOS 7 controller, if any, to invest in at this early stage?

All three are very different devices. The PowerShell, compatible with the iPhone 5, iPhone 5S, and 5th-gen iPod Touch (thanks to an included attachment. No iPhone 5C though), has some advantages over the other two, but overall it's hard to recommend for most players.

Design

In terms of overall build quality, the Logitech PowerShell is surprisingly solid. It feels heavy, but not overly so; it's actually the perfect weight to give it some heft, like an Xbox 360 controller, so it feels weighty and substantial in your hands.

Its rubbery surface is well-suited to a gamer's grip, as well, and the back has been shaped with a pair of well-placed ridges where your fingers will rest. The back and triggers have a great-feeling textured pattern as well.

Slotting the iPhone into the PowerShell is also rather ingenious. It doesn't slide apart like the Moga controller, so you'd think it might be a pain to jam the phone inside. But the PowerShell's lightning connector input jack rests in a pivot that swivels upward, so the parts don't strain when you snap your iPhone into the controller or take it out.

Once in, your iPhone or iPod Touch fits snugly into the PowerShell's frame. The device's speaker is amplified via a hollowed-out aperture in the PowerShell's face that funnels the sound directly to your face. But you can also still access the headphone jack with the included connector cord.

The phone's home button is still accessible, of course, and surprisingly so is the lock button on top - sort of. There's a small tab on the PowerShell's face, connected to a lever, that you can push sideways to reach the lock button. It's not exactly convenient, but at least it's there.

The Logitech PowerShell is slim, and that may be the one feature it has over the other iOS controller options. It could, theoretically, fit in someone's pocket. Not everyone's, but someone's. Better yet, you can throw it in your purse, backpack or briefcase and it won't take up much room there, either. The phone still retains its full functionality, and thanks to the PowerShell's slim and flat profile you can pretty much use it normally without too much added inconvenience.

Controls

But all of that is pointless unless the Logitech PowerShell is also a great game controller, and sadly this is where the gadget falls well short.

The first and biggest complaint is obvious: the PowerShell only features a single D-pad, lacking the dual analog sticks of its SteelSeries and Moga competitors (or even a single analog stick, for that matter). In the early days of iOS gaming, when 3D environments were rare, this may not have been a problem, but these days it's a make-or-break type omission.

Unfortunately, in this case it's more break than make. The PowerShell might have been salvageable if the D-pad was a decent replacement, but it's far from that. It's practically unusable - and it was a deliberate and well-meaning design decision on Logitech's part that made it that way.

The PowerShell's directional pad is analog. Theoretically that should make it an acceptable replacement for an actual analog stick, but in reality the analog D-pad makes the PowerShell a literal pain to use for any extended bouts of gaming. In most of the games we tested the D-pad required far too much pressure to register any input, and your thumb will get tired after just a half hour of wrestling with it, trying to get your vehicle, character or other avatar to move.

Many user reviews on Amazon note much the same thing, and a Logitech support account has taken to replying to these users with messages like the following:

"The reason the D-Pad feels that way is because it is a fully-analog input: It can detect both the button press and how hard you're pressing the button. Depending on how developers set up their individual games, they may require either more or less force for the button to be detected. That said, your feedback is valuable to us. We'll make sure to pass you message on to the PowerShell team."

That makes sense, but like many of the problems plaguing iOS 7 controllers, it's also unclear where to lay the blame. Is Logitech at fault for failing to explain how its D-pad works to developers? Are game developers to blame for ignoring the directional pad's analog nature and programming it like a traditional D-pad? Is it really Apple's fault for not having tougher or more uniform standards?

Whatever the reality, the PowerShell's lack of analog sticks and its poorly implemented analog D-pad make for a game controller that barely works. Many games, especially 3D ones, simply need an actual analog input to perform best. And even when a game should work better with the PowerShell, like a 2D platformer, you have to press the pad in so hard that you'll be fatigued in under an hour. That's simply unacceptable.

That one glaring gripe is even more unfortunate because the rest of the buttons are solid enough; the four face buttons are clicky and responsive, and the triggers too - when they're not getting stuck in the pressed-down position, that is. The left trigger is particularly prone to getting stuck - OK, forget it. It's clearly more than just the D-pad that's an issue.

Connectivity and battery

If you can ignore the control issues - and let's be clear, if you're spending $100 on a game controller then you shouldn't - the ease of connectivity and the added battery life the Logitech PowerShell provides your device will be a selling point.

Unlike the SteelSeries Stratus, the PowerShell doesn't require a Bluetooth connection, so you won't have to wrestle with that. Simply plug in your iPhone or iPod Touch and it's ready to go - the device will detect it automatically.

There's a small switch on the side to turn on the device-charging function. On average it charges about 10 percent in five minutes if you're not using your phone; with the screen locked it should get you up from a low battery to fully charged in under an hour.

As for the PowerShell itself, Logitech's official position is that its battery life will vary depending on the games you play. Frankly my thumb couldn't take playing it long enough to run it down, but it did last for over three hours of continuous play before we gave up.

Games

The list of games that support the Logitech PowerShell includes high profile names like Grand Theft Auto: San Andreas, Sonic the Hedgehog, Anomaly 2, Asphalt 8, Bastion, Galaxy On Fire 2, Limbo, Minigore 2, Sonic the Hedgehog 2, Knights of the Old Republic, Tomb Raider, and others.

There are dozens more, and that list will only increase as MFi program grows and iPhone controllers become more prevalent. That much has become clear in the months since iOS 7 was introduced.

I tried out several of them with the PowerShell. Sonic the Hedgehog 2 used it best, though like the others it suffered from the inescapable D-pad problem. Asphalt 8 and Into the Dead, a racing game and a first-person endless running game, respectively, were practically unplayable because of how hard you have to press the pad.

Games like Galaxy on Fire 2 and Air Wings Intergalactic work better in the sense that they accept the D-pad's analog inputs, so you don't need to press it so hard; but they'd still work better an actual analog stick, since using even a D-pad to control a ship moving in 3D space is awkward, even if it's an analog D-pad. Same goes for Eternity Warrior 2, a Diablo-like game that works better with an analog stick.

Minigore 2 and Dead Trigger 2, on the other hand, are games that really need a second analog input, whether it's a virtual one on the screen or the actual second analog stick that the SteelSeries Stratus and Moga Ace controllers possess. Minigore 2 lets you use auto-aim, but then you're just moving around and holding a button down - that's no fun. With Dead Trigger 2 you can move using the D-pad (still difficult), but you have to aim using the touch screen still, awkwardly stretching your right thumb over - so why bother at all?

We liked

When you first pick up the Logitech PowerShell and hold it in your hands, it feels like something you're going to like. The build quality is superior to the Moga Ace and the SteelSeries Stratus; it simply feels solid, like something you can use or throw in your bag without needing to worry about whether it's going to break.

We disliked

The analog D-pad sounds like a good idea until you realize it means every game that doesn't actually use analog controls makes you press it to its fullest depth, i.e. really hard, to do anything.

This is a fundamental design flaw that every single game developer would need to take into account for it to no longer be a problem, and with other, better options already available that's probably not going to happen.

Final verdict

The fact is this: if you care enough to buy a $100 iOS controller, you care enough to want a second analog stick. Or a first one, for that matter. This lacks features that are essential to its target audience, and thus is fundamentally flawed and impossible to recommend, despite some strong design in other areas.